1. Field of Art
The disclosure generally relates to the field of digital cameras, and more particularly to capturing synchronized images from multiple cameras.
2. Description of the Related Art
Digital cameras capture images using an electronic image sensor. Example image sensors use CCD (charge-coupled device) or CMOS (complementary metal-oxide semiconductor) technology. A CMOS image sensor contains photodiodes corresponding to pixels of a captured image. In one configuration, the photodiodes are arranged in rows and columns. To capture an image, successive rows of photodiodes are exposed and read over time. The direction in which rows of photodiodes are exposed over time is the rolling shutter direction. For example, if an image sensor reads a row of photodiodes after reading the row of photodiodes above it, then the image sensor has a downward rolling shutter direction. Portions of the image along the rolling shutter direction are exposed at later times. When capturing an image of a scene in which an object is moving or when capturing an image in which the camera is moving relative to one or more objects within the image, objects may appear blurred if the object moves in an image frame relative to different image sensor rows exposed at different times. Similarly, duplicates of an object may appear (e.g., an image of a spinning airplane propeller captured with a CMOS sensor). Such image artifacts are referred to as “rolling shutter artifacts.”
Three-dimensional (3D) images demonstrate depth information in a captured scene. One method for forming 3D images involves the combination of two or more two-dimensional (2D) images captured from different perspectives. An object's depth may be inferred based on the object's positions within the 2D images and based on the relative perspectives from which the 2D images were captured. When capturing a moving scene, the 2D images are taken simultaneously. Otherwise, capture objects moving relative to an image frame can appear at an incorrect depth in the resulting 3D image. When the rolling shutters of two cameras are misaligned, capturing the 2D images even simultaneously can result in rolling shutter artifacts and incorrect object depth determinations, as different portions of a scene are captured at different times. If the cameras do not capture the same portion of the scene at the same time, then any moving elements of the scene may appear blurred. To synchronize image capture, cameras containing the image sensors can be aligned along the direction of the rolling shutter using a six-axis pan-tilt camera mount, but aligning the cameras by this method is a time-consuming task, even for an experienced photographer.